The general goal of these investigations is to elucidate mechanisms of solute transport in the membranes of liver mitochondria and the relationships between these mechanisms and processes of cellular metabolism. Specifically, some investigations are focusing on the energy-linked uptake of inorganic cations by mitochondria. The kinetics of 42K and 28Mg flux into rat liver mitochondria are being examined in relation to a proposed non-electrogenic transport mechanism involving coupled movement of cations with hydroxyl ions. Some experiments are focusing on the interaction of the K ion ionophore, valinomycin with mitochondria isolated from a mutant yeast strain which exhibits resistance to this ionophore. Other experiments are examining the mechanism of transport of the urea cycle intermediate, ornithine into rat liver mitochondria.